Aside from the conventional tow truck which incorporates a winch, a power take-off mechanism connecting with the transmission of the truck and latching structure to lock the winch for towing, there have been attempts in the prior art to provide a vehicle designed for one type of use with structure whereby that vehicle may be utilized in a second mode of operation. A rather recent patent, namely, U.S. Pat. No. 4,000,823 to J. Aquila describes a vehicle commonly characterized as a "pick-up" truck which is provided with a towing crane, portions of which are permanently mounted in the bed of the vehicle. Aquila indicates that portions of the towing crane, as for example, the tow bar, front boom section and rear boom section necessary for lifting and towing may be removed from the permanently mounted portions which remain in the bed when the towing crane is not in use. The lifting and towing operation is accomplished by the tow bar and boom sections as well as a power cylinder connected between the boom sections and the permanently mounted portions. The power cylinder has no other function and Aquila, also, suggests that the rod of the power cylinder may be retracted fully so that the power cylinder may nest with the other portions in the bed of the vehicle.
The prior art also includes other forms of vehicles which support structure capable of use in the lifting and towing of a second vehicle. For example, U.S. Pat. No. 2,449,146 to C. N. Ryan, includes a lifting and towing structure which is secured to the bed or frame of the vehicle for purposes of converting the vehicle to a wrecking truck or vehicle-pulling car. The Ryan structure utilizes an hydraulic cylinder which through a piston rod imparts movement to the lifting frame which is capable of pivoting about a pair of spaced pivot points located forwardly (toward the vehicle cab) of a stationary frame structure secured to the bed or frame. Through movement of the lifting frame, the boom may be raised. Thereafter, the lifting frame is latched in the boom raised position for purposes of towing a second vehicle. In U.S. Pat. No. 2,481,223 to B. M. Johnson, a lifting and towing mechanism is attached to the fifth wheel of a tractor in the same manner as a conventional trailer is attached to the tractor. The lifting and towing mechanism includes a section which pivots about the end of the tractor frame and a boom which is adjusted both longitudinally and horizontally relative to a stationary portion of the towing mechanism. The boom is controlled in movement by an hydraulic lift.
U.S. Pat. No. 3,298,744 to A. J. Keim discloses a mechanism which is utilized as a trailer hitch in the towing of an unpropelled vehicle, such as a grain wagon. The trailer hitch is described as being connected to the underside of the bed of a dump truck in a position so as not to interfere with the hydraulic mechanism provided for raising the bed or with the structure about which the bed of the dump truck pivots in a dumping operation. The trailer hitch extends downwardly from a position to the rear of the bed and a hitch plate is attached to its end. A tubular sleeve is supported by a bracket carried on the frame to the underside of the bed and a rod connected at one end to the trailer hitch is telescopically received into and out of the sleeve thereby to permit movement of the trailer between an operative and a collapsed, stored position.
None of the prior art is directed to, nor does it provide, a solution of an alternative capability of use of a vehicle in the capacity either of a truck, such as a dump truck and also as a truck for transport of a load or as a tow truck utilizing for lifting and towing an hydraulic cylinder which also functions to provide for movement of the bed of the vehicle when employed as a dump truck. Thus, the hydraulic mechanism has a dual function and through implementation of an hydraulic cylinder capable of providing positive action in both directions of movement of a piston rod the bed of the vehicle is caused to pivot about a pivot axis to an inclined dumping position and to be positively returned to a horizontal non-dumping position. These movements make it possible to employ the vehicle in the dual capacity, as will be fully explained below. The conventional tow trucks which utilize a winch and the allied power mechanisms for lifting and towing are incapable of satisfactorily serving in a dual capacity, such as contemplated herein for reason that the power mechanisms and winch leave little or no additional space in the bed of the tow truck.